Stabilized organic compositions containing aralkylated alkoxy phenols



United States Patent STABILIZED ORGANIC CONIPOSITIONS CONTAIN- lNGARALKYLATED ALKOXY PHENOLS David W. Young and Fred W. Banes, Westfield,N. J., as-

sigors to Esso Research and Engineering Company, a corporation ofDelaware No Drawing. Application January 8, 1952, Serial No. 265,534

9 Claims. (CI. 44-78) of alkoxy phenols which have been furtheralkylated with Thus, for example, in the oil refining industry, in orderto prepare lubricating oils of superior quality, it is generallynecessary to stabilize the oil against degradation which normally occursdue to oxidation of the hydrocarbon components. In general, hydrocarbonmixtures falling in the lubricating oil boiling range, if unstabilized,will over a period of time under certain conditions be subject to gumformation, sludge formation, the formation of acids and the formation ofobjectionable color bodies. a

It is also known that synthetic rubbers undergo changes due to furtherpolymerization ordegradation due to depolymerization on exposure to airand consequently yield on vulcanization inferior products unless thereis incorporated therewith at time 'of synthesis a compound whichstabilizes the synthetic rubber by largely preventing oxidation,degradation and/or cyclization of the chain molecules present in thepolymer structure. Natural, as well as synthetic, rubbers require ananti-oxidant present in the vulcanizate in order that finished rubberproducts remain stable toward oxidation and heat during their usefullife.

Alkoxy phenols have been employed as stabilizers for unstableorganiematerials but many of these phenols suffer from the disadvantageof possessing only limited solubility in hydrocarbon materials andexcessive solubility in water. This limited solubility in hydrocarbonsnecessitates the use of an expensive auxiliary solvent. 7

It has now been found that alkoxy phenols which have been furtheraralkylated, i. e., reacted with aromatic compounds containingunsaturated side chains, are extremely eifective oxidation inhibitorsand stabilizers for materials which usually degrade in the presence ofair and/ or heat. In addition, the compounds of this invention do notsuffer from the above-listed disadvantages of the simple alkoxy phenols.

Those compounds, whichare believed to be new chemicals, in which thealkoxy group has from 1 to 4 carbon atoms, e. g., the methoxy, ethoxy,propoxy and butoxy, and the aralkylating compound is styrene,alpha-methyl styrene, or alpha-methyl or p-methyl styrene, areespecially efiective.

The anti-oxidant products of this invention are solid orliquid innature, depending upon the temperature at which they are held. Theirstructure is illustrated in Formula I below:

OH CH3 Formula I wherein R is an alkyl radical having from 1 to 4 carbonatoms, R" is a radical selected from the group consisting of H andmethyl radicals, R' is a radical selected from the group consisting of Hand radicals and R"" is hydrogen or a methyl group.

The styrene-type substituent may occur once or twice in the molecule ofthe finished product depending upon the extent of alkylation. It ispreferred to have two styrene-type groups linked to the alkoxy compound.

It should be noted that the alkoxy group occurs para to the hydroxylgroup, which, in turn, is ortho to the styrene linkages, It is thisparticular configuration which is believed to impart the desiredcharacteristics to the products of this invention. The compoundsutilized for the anti-oxidant purposes of this invention are largelywater-insoluble and oil-soluble, a desirable combination ofcharacteristics.

The compounds of this invention can be prepared in general byaralkylating an alkoxy phenol in the presence of a solvent such asheptane, benzene, toluene, tetrachloroethane, kerosene, etc., withstyrene or alpha-methyl styrene, etc., in the liquid phase at atemperature in the range of 30 to 80 C. Approximately equimolarconcentrations of reactants are employed if a monoalkylated product isto be obtained and approximately a 2 to 1 molar ratio of styrene isemployed if the preferable dialkylated product is to be made. Anacid-type condensation catalyst such as sulfuric acid, BFs, BFs-ethercatalyst complex, BFs-phenol complex, AlCla, AlBrs, TiCl4 is employed inan amount of about 0.1 to 5 wt. percent. The solvent is then evaporatedleaving the anti-oxidant product. The product is purified of residualcatalyst by Washing with aqueous bicarbonate or caustic solution.

A preferred method is to percolate the reaction mixture through anadsorbing clay such as attapulgus clay.

The following examples are given to illustrate this invention andinclude both the preparation of products of this invention and testresults on their use as antioxidants.

EXAMPLE I One mol of 4-methoxy phenol was alkylated in heptane solutionwith one mol of styrene using H2804 catalyst at 50 C. to form Z-(alphaphenyl ethyl) 4-methoxy phenol. The amount of catalyst used was 2 weightper cent and the time interval of alkylation was between 2 to 4 hours.After the alkylation had taken place, the product was washed with water,sodium bicarbonate solution, water, and dried. The anti-oxidant had aboiling point of l45150 C. at 8 mm. Hg.

EXAMPLE II In this example the evaluation test used was the ASTMOxidation Stability Test designated as ASTM-D-525-46.

This test essentially consists of placing 50 cc. of the compositionbeing tested in a bomb, after which oxygen is added to provide apressure of about 100 lbs. p. s. i. g. This bomb is then heated to about100 C. and the pressure in the bomb is determined at -minute intervals.When sufiicient time has passed so that the pressure drops two pounds p.s. i. g. in 15 minutes, the test is discontinued and the time requiredto reach this condition is recorded at the induction period or the ASTMbreakdown time and is ordinarily given in minutes. A material subjectedto this test which is markedly unstable to oxidation will result in anASTM breakdown time of about one hour, while an oxidation stable mixturewill be characterized by breakdown times of 150 minutes or longer. Twopounds per 5,000 gallons of the compound prepared in Example I gave anASTM breakdown time of 525 minutes in a cracked leaded premium gasoline.The control gave a breakdown of 135 minutes.

This example illustrates the marked improvement in anti-oxidant efficacyobtained by the compounds of this invention.

EXAMPLE III 4 e. g. the 4-methoxy phenol alkylated with 2 mols ofstyrene exhibited an ASTM value of 50% more than the same alkoxy phenolalkylated with 2 mols of isobutylene.

EXAMPLE IV I The compounds of this invention were tested in a lime basegrease for anti-oxidant activity. The Norma Hoffman Oxidation Test wasused. This test comprises placingithe grease in glass sample dishes inan oxidation bomb at 210 F. and .110 lbs. of initial oxygen pressure,using 20 gram samples of the grease. The pressure drop is measuredperiodically. The results were as follows:

The same ASTM test indicated in Example II was performed on otheraralkylated alkoxy phenol compounds 51b. 101b. 15lb. 201b, r n t' d th dt The 1t 15 11 Drop, Drop, Drop, 0 t iS lnven ion an 0 er pro uc s. resus o ow. Hm Hrs Hrs Hm Breakdown B nk grease 44 172 188 Anti-oxidant;Time in Grease 0.6% etho y p e ol Minutes alkylated with one mol ofstyrene; 172 199 240 360 30 8 The results indicatehow grease wasstabilized by the 4-Ethoxy phenol. 290 products of this invention.A-Butoxy phenol 250 2,6 Di-t-butyM methoxy phenoL 300 EXAMPLE VI2-n-butyl-4-methoxy phenol 280 i- P The p unds of this invention weretested for anti- 2-t-But -4-e oxyp eno phenolalkylated withl moloistyren oxidant effect on Paracrll-26 (a butadlene-acrylonrtrile4-Methoxy phenol alkylated with 2 mols of styrene 440 synthetic rubber).The results fOllOW: 4-Methoxy phenol alkylated with 1 mol ofalpha-methyl 80 G l P l 26 bb Styrene 0 e ormation in aracri r 4-Methoxyphenol alkylated with 2 mols of alpha-methyl f d at 140 for 14 iii t lili l ll; ltd 'thi l Tlh ethT 410 ays 6 8. a 0 W). 1110 0 a 3-11]. 4 mlgir 'sfimfifl y p y 370 [26%nitr1lemcopolymer] -Methoxy phenol alkylatedwith 2 mols of alpha-methyl-p- 4 iii t li yl l r i li'l 't t'itlii"iTlTiri'ElYi' 400 Percent N A d Percent Color of e ox one a ya e W1mo 0 up ae y mm of t styrene ar fd 1 mol of alpha-methyl-p-methylstyrene 385 Anti-oxidant n 1 1 an Gel Rubber 4-Ethoxy phenol alfiylagegWi g mol of sttyrene 4-Ethox eno a a e w moso s yrene 4 1mm; phenol alliylated with 2 mols of alpha-methyl 1 9 w phenol alkylated 55 LightBrown,

styrene 280 with 1 .mol of Styrene. Z-Methoxy phenol alkylatedwithlmolotstyrene 160 0 None. s9 .Blaok.

Several points should be particularly noted from these data besides theexcellent anti-oxidant effectiveness of the compounds of this invention.These compounds were at least as effective as the simple alkoxy phenolsand in most cases much more efiective. This is important because thecompounds of this invention do not exhibit the undesirable watersolubility and 10% NazCOs solubility of the simple alkoxy phenols. Watersolubility results in the leaching of the simple alkoxy phenols fromthegasoline when the latter comes in contact'with water.

Another point to be notedis the criticality of the spatialconfiguration, i. e., that the alkoxy group inthe compounds of thisinvention be in a para position with respect to the hydroxyl group. Thusthe 4-methoxy phenol aralkylated with one mol of styrene exhibited anASTM breakdown of 585, whereas the 2-methoxy phenol alkylated with onemol of styrene exhibited an ASTM breakdown of 160 or a decreased time of73%.

In addition, these data bring out that the anti-oxidant etficacy of thecompounds ofthis invention decreases with increasing chain length of thealkoxy group. This is completely surprising in view of the fact that thereverse phenomena occur with conventional anti-oxidants such as2,6-di-t-butyl-4-methyl phenol, 2,6-di-t-butyl-4- ethyl phenol and2,6-di-t-butyl4-butyl phenol.

;In addition, the compounds .of this invention exhibit better activitythan ordinary ralkylated {alkoxy phenols,

The Paracril was clearly improved by the product of this invention.

EXAMPLE VII The physical characteristics of various compounds ofthisinvention were determined. These results are listed below:

Compound Boiling Point;

0. at 4 mm. Hg.

20020l O. at 3 mm. Hg.

-ltt liethoxy phenol alkylated with 1 mol :5 yre I 4 Methoxyphenolalkylated with 2 mols styrene, product known as 2,6-diphenylethyl-4-methoxy phenol.

4-Methoxy phenol alkylated with 1 mol alpha-methyl-styrene.

4-Methoxy phenolalkylated with Z mols ot-alpha-methyl styrene.

C. at 4 mm. Hg.

208 C. at 3 mm. Hg.

It is also proposed that the aralkylated alkoxy phenol anti-oxidants ofthis invention be employed to stabilize organic compounds such asmineral oils, synthetic ester lubricating oils, lubricating oils andparticularly that they should be used to stabilize the class of oilsknown as turbine oils. Turbine oils are highly refined lubricating oils,having a range-in Saybolt viscosity at 2l0 F. from about 43 to 145, towhich are added suitable anti-oxidants, rust preventers, pourdepressants, V. I. improvers, metallic soaps and other additives.

The synthetic rubbers whichma'y be stabilized in accordance with thisinvention in addition to GR-I (isobutylene-diolefin polymer) rubber arethe polymers consisting predominantly of a polymerizable conjugateddiolefin having four to six carbon atoms, e. g., 1,3- butadiene,isoprene,2,3-dimethylbutadiene, 2-chlorobu-' tadiene-1,3, piperylene,2-methylpentadiene-1,3, and the like; hence, synthetic rubbers of theabove class include polymers of these materials and also copolymersprepared by the polymerization of monomer mixtures comprising a majorproportion of such a polymerizable diolefin and also containing a minorproportion of other monethylenically unsaturated compoundscopolymerizable with the diolefin such as methyl acrylonitrile, methylmethacrylate, styrene, alpha-methyl styrene, vinyl naphthalene, vinylketones, vinylidene chloride, diethyl fumarate, vinyl pyridine, and thelike. Natural vulcanized rubber is also stabilized by the compounds ofthis invention.

The incorporation of the aralkylated alkoxy phenols with the syntheticrubber may be carried out simply by adding the compounds either in thepure form or in solution, suspension or emulsion to the solid syntheticrubber in a water dispersion, or during the milling operation, or to alatex containing the synthetic rubber dispersed in an aqueous mediumsuch as is ordinarily obtained by an emulsion polymerization process.

The amount of the indicated ingredients added to the normally oxidizablematerial in order to prevent oxidation varies with difierent materials.

In general, the amount that has to be added to the normally oxidizablematerial represents only a small proportion of the normally oxidizablesubstance, i. e., 0.0003-5 weight per cent based on the normallyoxidizable material.

Typical formulations are as follows with the weight per cent figurebased on the normally oxidizable substance:

Gasoline0.l to 5 lbs. present per 5,000 gal. of gasoline (approximately.00030.l5 wt. per cent).

Lubricating oils0.02 to 10% by weight.

Rubbers and plastics0.1 to 5% by weight.

The compounds of this invention may be utilized in mixtures or inconjunction with other anti-oxidants in order to obtain desirablecombinations of properties. Among the other anti-oxidant materials whichmay be so employed are phenyl-beta-naphthylamine, naphthols, substitutednaphthols, substituted phenols, substituted catechols, substitutedhydroquinones, alkyl phenol sulfides, ketone-amine condensationproducts, aralkylated and alicyclic substituted phenols, and the like.Due to the fact that the aralkylated alkoxy phenols have good color,they may be mixed with 2,6-ditertiary-butyl-4- methyl phenol in rubberor resin compounds to form light colored stocks.

The anti-oxidant compounds of this invention have many advantages, amongwhich are their extreme potency, ease of preparation, good colorretention, nonstaining and odorless character and volatility.

The formula presented above in Formula 1 represents what is believed tobe the correct structure of the compounds synthesized, i. e., thecompounds produced during the course of the synthesis in the muchgreater proportion and those to which the anti-oxidant activity isbelieved to be attributable. It is possible, however, "that minoramounts or traces of isomeric compounds are also produced. Thesevcompounds also contain the particular configuration referred to above,which is believed to impart the desired characteristics to the productof this invention.

It is to be understood th'at't he invention is not limited to thespecific examples which have been offered merely as illustrations, sinceother derivatives can be prepared, and that modifications may be madewithout departing from the spirit of the invention.

What is claimed is:

1. A composition of matter comprising an organic hydrocarbon materialnormally subject to oxidative changes containing as an anti-oxidant0.0003 to about 5% by Weight of an aralkylated alkoxy phenolcorresponding to the general formula 0H CH2 wherein R is an alkylradical having from 1 to 4 carbon atoms, R" is a radical selected 'fromthe group consisting of hydrogen and methyl radicals, R" is a radicalselected from the group consisting of hydrogen and EH: I i" RI!!!radicals and R"" is a radical selected from the group consisting ofhydrogen and methyl radicals.

2. A composition as in claim 1 in which R", R'" and R" are hydrogen.

3. A composition as in claim 1 in which R is a methyl radical, R" andR"" are hydrogen and R' is the alpha phenyl ethyl radical.

4. A composition as in claim 1 in which R and R" are methyl radicals, R'is the alpha methyl alpha phenyl ethyl radical and R"" is hydrogen.

5. A cracked gasoline containing as an inhibitor against oxidativedeterioration an aralkylated alkoxy phenol corresponding to the generalformula OH CH:

R III wherein R is an alkyl radical having from 1 to 4 carbon atoms, R"is a radical selected from the group consisting of hydrogen and methylradicals, R is a radical selected from the group consisting of hydrogenand I RI!!! radicals and R" is a radical selected from the groupconsisting of hydrogen and methyl radicals, said alkoxy phenol beingpresent in an amount corresponding to approximately 0.01 to 5 pounds per5,000 gallons of gasoline.

6. A composition as in claim 5 in which R" and R' are hydrogen.

7. A composition as in claim 5 in which R is a. methyl radical, R" andR" are hydrogen and R is the alpha phenyl ethyl radical.

8. A composition as in claim 5 in which R and R" are methyl radicals, Ris the alpha methyl alpha phenyl ethyl radical and R'"' is hydrogen.

9. A composition of matter comprising an organic material normallysubject to oxidative changes containing radicals and R"" is a radicalselected from the group as an anti-oxidant from about 0.0003 to about 5wt. consisting of hydrogen and methyl radicals. per cent of anaralkylated alkoxy phenol corresponding 7 t0 the general formulaReferences Cited in the file of this patent 011 Z 5 2 UNITED STATESPATENTS I T 2,285,625 Taylor et a1. June 9, 1942 R "I, 2,326,702 Tayloret a1 Aug. 10, 1943 R 2,591,651 Young Apr. 1, 1952 OR 10 wherein R is analkyl radical having from 1 to 4 carbon FOREIGN PATENTS atoms, R" is aradical selected from the group con- 523,696 Germany May 4, 1931 lsisting of hydrogen and methyl radical s, R is a radical selected fromthe group'consis ting of hydrogen and OTHER REFERENCES 03, Dodds et al.:Nature, page 996, June 13, 1936. (Copy A g in Sci. Lib.) Bl

9. A COMPOSTION OF MATTER COMPRISING AN ORGANIC MATERIAL NORMALLYSUBJECT TO OXIDATIVE CHANGES CONTAINING AS AN ANTI-OXIDANT FROM ABOUT0.0003 TO ABOUT 5 WT. PER CENT OF AN ARALKYLATED ALKOXY PHENOLCORRESPONDING TO THE GENERAL FORMULA